Seat belt devices of vehicles and the like generally have a construction wherein a webbing is wound on a retractor provided with an emergency locking mechanism. In this kind of seat belt device, when the vehicle crashes or stops suddenly the emergency locking mechanism detects acceleration changes caused by collision impact forces and operates to stop the rotation of the reel shaft on which the webbing is wound so that withdrawal of the webbing is arrested and the passenger's body is restrained.
Examples of publications relating to this type of retractor include JP U 5-32176, U.S. Pat. Nos. 5,137,226, 5,154,368, 5,156,356, and numerous others.
To ensure their safety, seat belt retractor strength requirements are stipulated by law. With the kind of conventional mechanism described above, which uses a pawl having one tooth, it has not been possible to reduce the size of the ratchet wheel while still satisfying these strength requirements, and consequently it has naturally also been difficult to reduce the size of the retractor.
However, in recent years, 3-point type seat belts having retractors equipped with emergency lock mechanisms have also come to be widely used for the rear seats of passenger vehicles, and, from the point of view of the space required for installing the retractor, the need to reduce the size of the retractor has become greater.
A first object of the present invention is to provide means by which the retractor can be made more compact.
The present invention also relates to a so-called direct-lock retractor, wherein in a retractor equipped with an emergency locking mechanism, during an emergency, as well as the webbing reel shaft being locked the webbing that has been withdrawn from the webbing reel shaft is also clamped so that the withdrawal of the webbing is arrested.
In general, emergency-lock type seat belt retractors are designed to restrain the body of the wearer of the seat belt during an emergency by arresting the withdrawal of the webbing by locking the webbing reel shaft.
However, with this type of retractor there has been the problem that even when the rotation of the webbing reel shaft is locked, when the webbing is subjected to a large load the webbing itself wound on the webbing reel shaft becomes more tightly wound and a further short length of webbing is withdrawn.
In order to solve this problem, clamping means has been mounted with the part of the webbing that has been withdrawn from the webbing reel shaft so that the withdrawal of the webbing from the webbing reel shaft can be arrested by the clamping means moving in cooperation with the webbing reel shaft locking means and clamping the webbing.
A second object of the present invention is to provide a retractor in which, in basically the same actuation mechanism as a conventional retractor, the moving distance of a first clamp member is increased without the pivot angle of an actuating lever being increased, so that the webbing is clamped rapidly.